Airplane propeller



S. HEATH AIRPLANE PROPELLER July 14, 192s.A 1,545,560

Filed Aug, 6, 1924 Patented July 14, .1925.

PA'iifnrr OFFICE.

SPENGEB HEATH, F ELKBIDGE, MARYLAND.

AIBPLANE rnoPELLEn.

application mea' august e, 1924. serial in. 730,475.

To all 'whom t may concern:

Be it known that I, SPENCER HEATH, a

i citizen of the United States, residing at Elkridge, 'in the county of Howard and State of Maryland, have invented certain new and useful Improvements in ,Airplane j Propellers, of which the following is a specification.

This invention relates to airplane propellers and has particular reference to propellers made of wood or other non-metallic material in which it is necessary to protect the propeller' blades by metal sheathing covering those portions of the blades most exposed to wear. l

The objects of this invention aieto pr0- vide means for fitting the metal more closely and rml to the wood, especially on its convex si e, to provide more secure means for joining the metal at the edges of the blades and to provide more durable protection of the edges of the blade against damage With these and other objects in view I have invented the improvements described in this specification and illustrated by the attached drawing, in which:

Figure 1 is a plan view;

Figure 2 is a section on line 2-2 of F.` 1; Figure 3 is a section on line 3 3 of ig. 1; and

Figure 4 is a section showing the method of metal sheathing heretofore employed.v

For ten or twelve years it has been the practice to attach the sheet metal to the blade faces by rivets or screws with the metal extending somewhat beyond the edges of the blades and to bend the metal over 'the ed es of the wood in plain laps as shown in 1g. 4, the metal being held together onl by solder between the portions lap ed. nder this practice there are two specia difficulties:

First, in applying the metal and `joining it at the edges of the blades there is no practicable means for stretching and drawing the metal tightly and smoothly over the surface of the wood, the consequence being that there is cushion-like effect between the rlvets or screws and at the lapped edges the metal does not draw firmly down against the wood, thus making the edge of the propeller insubstantial and subject to dents. Second, the soldered lap joints frequently crystallize and give way under the intense vibration of 1500 to 2000 and upwards revolutions per minute. i

To obviate these diiiculties I use a double lock seam for joining the metal at the edges of the blades. This seam is clearly shown at numeral 10 in Figs. l, 2 and 3. The metal is first secured to the wood in that port-ion remote from the part to be seamed i as by the line of rivets 11 (with few or only temporary fastenings near the edge to be seamed) The edges of the upper and lower sheets of metal 12 .and 13 `are carried forward together in a straight '-line as shown by the vdot-ted lines at 14 and 15, the lower sheety projecting further than the upper and turned back upon it as shown dotted at 16 to make a three-ply portion beyond the edge of the blade. This is called the first turning. The second turning consists in folding the three-ply dotted portion back against thel upper portion 12, thus completing the lock joint as shown at 10. This second turning has the im ortant eHect of drawing and 'stretching t e portions 12 and 13 tight and firm over the wood and bringing the seam itself hard up against the edge of the blade with the firm stiffness and 'protection of four thicknesses of metal instead of two.

In practice, the thickness of metal and the size of the seam 10 is much smaller than in my illustration so that the seam imbeds itself partially into the edge of the blade with llttle if any-distortion of the general contour. This stretching and double locking seam has been found of itself sufficiently strong to hold but its stren h can be further increased by running so der in between the folds of the seam, 1n which ca se the solder at the edge of the seam 17 .further im roves the contour.

n account of the metal crystallizing when put in single sheets, I refer to apply the metal on each side of the lade in several sections in accordance with my U. S. Patent No. 1,339,886, and with overlapped edges as shown at 18 and 19 in Fig. 1.

The stretching and locking seam is of peculiar value as applied to the leading edge of the blade (which is most exposed to injury and wear) but when both edges of the blade where the metal is applied are considerably curved the stretchlng and locking seam is formed on both edges of the blade. However, where one edge is straight or nearly so I prefer making the tip section for both sides of the blade in one plece and bending it without a seam over the straight edge of the blade as shown at 20 in Figs. 1 and 3 and forming the lock. seam along the other edge of the blade and around the end.

This bending Without seam is most desired Where the trailing edge of the blade is the straight edge, the protective interlocking seam then being formed, asV shown on the drawing, on the leading edge, which is the edge most subject to wear.

While I have described my invention as relating to Wooden blades protected by metal sheets it is to be understood as applying' to -any materials that can be manipulated in the general manner described.

Besides the advantages of close fitting sheets and harder and more durable edges a further value of this method of sheathing lies in that actthat by it the sheathing can be adequately secured to the blades Without employment of an solder in the seams this not only making t e Work more economical but opening up the employment as blade sheathing of such materials as duralumin7 and other light and strong alloys or other desirable materials which it, may not be practicable to unite by soldered seams.

Having fully described my invention and the method of its practice, What I claim is:

l. A sheathed propeller blade including sheet material applied to both sides ot' the blade and joined at the edge of the blade by a double turned seam providing four thicknesses of sheet material at the seamed portion. y

2. A sheathed propeller blade including sheet material applied to both sides of the blade and joined at the leading edge of the blade by a seam providing four thicknesses of the sheet material.

31 A sheathed propeller blade including sheet material applied to both sides of the bl-ade, the material being bent seamless over one edge of the blade and joined by a'seam on the other edge of the blade.

4. A sheathed propeller blade including sheet material ap lied to both sides of the blade, the materia being bent seamless over that edge of the blade having the lesser exposure to injury and wear and being joined y a -seam providing four thicknesses of the sheet material at that edge of the blade having the greater exposure to injury and wear.

5. A sheathed propeller blade including sectional sheet material applied to both sides of the blade and joined at the leading ed e ot" the blade by a seam providing four thicknesses of the sheet material.

6. The method of sheathing propeller blades Which consists in appl ing sheet material to both sides of the blades With the edges of said material projecting beyond the edge of the blade, attaching the material to the blade at some distance from the projecting edges and doubling said edges together in such manner as to stretch the material between its attachment to the blade and its projecting edges and at the same time to form an interlocking seam.

7. A sheathed propeller blade including sheet material applied to both sides of the blade and joined at the edge of the blade by a folded seam providing a plurality of thicknesses of sheet material at the seamed portion.

In testimony whereof, I hereunto aiiix my signature.

SPENCER HEATH. 

